1. Field of the Invention
This invention relates to coating equipment comprising a coating apparatus for applying a coating material to an object.
2. Description of the Related Art
Among methods used to apply a resist to a semiconductor wafer, as an object to be coated, that disclosed in Japanese Patent Disclosure No. 52-144971 is well known. According to this method, a resist is applied to a semiconductor wafer by a spin coater installed in a clean room. A semiconductor wafer is held on a spin chuck by vacuum chucking with its surface to be coated up. The spin chuck is positioned in a cup having at the top end an inlet port for introducing a vertical laminar flow from the clean room. While the wafer is rotated at high speed by a motor connected to the spin chuck, a resist is dispensed onto the center surface of the wafer and is spread out over the entire surface by centrifugal force.
However, when a resist is applied to a wafer by an apparatus such as described above, there is a problem that the change of the resist temperature on the resist layer applied causes the wafer to be nonuniform in thickness.
A technique has been developed with the aim of solving this problem, for example that disclosed in Japanese Patent Disclosure No. 61-125017. According to the technique disclosed therein, the resist temperature is prevented from changing by it being controlled during coating on the surface of a semiconductor wafer.
For the step of developing the pattern-exposed resist layer on a semiconductor wafer, a method has been devised in which the semiconductor wafer is held surface up on a spin chuck provided in a cup having at top end an inlet port for introducing a vertical laminar flow from a clean room by a vacuum, and a developer is supplied from a spray nozzle onto that surface of the wafer to be developed while the wafer is either rotated at low speed by a motor connected to the spin chuck or is stationary. Then, the wafer is rotated at high speed by the motor, to spin off the remaining developer by centrifugal force. Also in this case, there is a problem that nonuniform development occurs in the developed pattern on the wafer due to the temperature change of the developer as in the resist coating described above. A method has been developed with the aim of solving this problem, the method comprising the step of applying a developer by controlling the temperature of the developer to restrain the temperature change of the resist.
However, when a resist or a developer is applied on a semiconductor wafer in a cup with a vertical laminar flow introduced from the clean room, as described above, the resist and developer supplied to the wafer is affected by the temperature and humidity of the atmosphere in the cup even if the temperature of the resist or developer is controlled. Thus, the change in the temperature and humidity of the atmosphere in the cup makes it impossible to obtain a desirable resist thickness and a desirable developed pattern or to achieve desired uniformity in the resist thickness and pattern development. This results in low yield and productivity.
As for the technique for stabilizing the atmosphere around a wafer, there is one disclosed in Japanese Patent Disclosure No. 60-152029. This technique will be described referring to FIG. 1. In FIG. 1, semiconductor wafer 1 held on spin chuck 5 is totally enclosed by cover 4 comprising lower cup 3 and upper cup 2. Under this condition, a resist is dropped to the center of wafer 1 from nozzle 6. Then, the solvent contained in the resist evaporates. Since an inner space of cover 4 is saturated with the solvent vapor, the temperature and humidity around semiconductor wafer 1 are constant. By rotating wafer 1 under this condition by motor 7, it can be expected that a uniform resist layer is formed on the surface of wafer 1.
With this technique, however, there is a possibility that the resist or developer spun off by the rotation of wafer 1 sticks to the internal wall of cover 4. When the substance sticking to the wall is thickly stacked, the substance exfoliates by a small force and contaminates the atmosphere in the cup and dust thus produced adheres to semiconductor wafer 1. As the integration in wafer 1 advances from 256K bits to 1M bits or 4M bits, it becomes necessary to improve the cleanness of the atmosphere. However, the above-mentioned technique has a problem that the dust adhesion to the wafer, which is inevitable with this technique, inhibits a required cleanness from being achieved, resulting in low yield and productivity.